In recent years, there have been developed, as a preparation for intravenous drip, soft bag preparations wherein a medicine for injection is preliminarily diluted and filled in a flexible container such as plastics. The soft bag preparation has been accepted as being useful because of its excellence in disposability over glass bottles and ampules along with the convenience and readiness in use.
It is known, however, that part of medicines including nitro glycerine, protein-containing preparations such as albumin, hormone and the like, a hyaluronic acid preparation, preparations of vitamins, trace elements, insulin, anticancer agents, radical scavengers and the like adsorb on or penetrate into base materials for medical container including ordinary polyolefin resins (PO resins) polyethylene (PE), polypropylene (PP) and the like, and vinyl chloride resin. Hence, effective components in a content fluid may be adsorbed, or interactions between additives or low-molecular-weight components present in the base material and the content fluid may occur, thereby presenting a problem on the development of soft bag preparation.
From this point of view, there is proposed, as described, for example, in JP-A 2004-298220 (Patent Document 1), the use of cycloolefin resins (COP resins) as a resin that is free of medicinal adsorption or penetration.
In JP-A 2008-29829 (Patent Document 2), application and development of COP resins, which have been hitherto used as a prefilled syringe container, to soft bags is disclosed.
This container makes use of a polyethylene resin (PE resin) as an innermost layer, for which while increasing drop impact strength as a container and keeping satisfactory strength for use as a liquid storage container, certain effects of preventing the component adsorption and the interaction with a content fluid have been recognized. In this connection, however, because of the polyethylene resin used as innermost layer, the effects of preventing the component adsorption and the interaction with a content fluid are worse than with the case using conventional glass containers, thereby not leading to satisfactory dissolution of the problem.
COP resins are greater in molecular weight than low-density polyethylene and the like, are more linear and have a bulky molecular structure based on the cyclic hydrocarbon group in the molecular structure, so that limitation is placed on the thermal motion of the molecular main chain. As a consequence, where formed as a film, the resin is liable to provide a hard, brittle film. Accordingly, for use as a base material film of soft bag, usual practice is to laminate this with a flexible PO resin such as a PE resin.
For instance, in JP-A 2005-254508 (Patent Document 3), there is disclosed a packaging pouch made of a laminated film having a PO resin as an outer layer and a COP resin as an inner layer. It is stated that because high pressure steam sterilization treatment is possible and component adsorption can be suppressed, the pouch is adapted for use for injection preparations that are liable to be adsorbed.
In JP-A 2006-081898 (Patent Document 4), there is described a soft bag wherein a layer made of a COP resin or a resin containing a COP resin and a layer of a polyester resin or PO resin are laminated.
Incidentally, it has been accepted from the standpoint of component adsorptivity that soft bags making use of these multilayered films are beneficial when using a COP resin layer as an innermost layer. On the other hand, these soft bags are usually provided with a discharge port (port) for discharging a medicinal solution. With respect to a discharge port member, it is considered in view of weldability with a COP resin of an innermost layer of bag that it is necessary to use a discharge port member formed likewise of a COP resin.
However, when forming the discharge port member made only of a COP resin, which is much more expensive than PO resins, an amount of the resin used becomes great, resulting in poor economy. As stated hereinbefore, the COP resin per se is hard and brittle, so although the mutually welded portion of COP resin members is high in weld strength, it is brittle against impact and flexion, with the attendant problem that when dropped, such a discharge port is liable to suffer breakage therearound. Moreover, when a cap for covering a rubber stopper is welded so as to prevent the rubber stopper from coming off, a problem has also been involved in the cost of the cap and the brittleness at the welded portion. Where the cap per se made of COP is dropped, the impact is concentrated at the cap portion, leading to the high possibility of breakage. Accordingly, there has been demanded the development of a soft bag that is free of medicine adsorption and penetration and is unlikely to suffer breakage when subjected to impact such as dropping.
With respect to the brittleness of the discharge port per se, it is described in JP-A 2005-254508 (Patent Document 3) that flexibility is imparted by formulating a thermoplastic elastomer in a COP resin. In this JP-A 2005-254508 (Patent Document 3), it is stated that there may be used a double molded port making use of a COP resin as an innermost layer and linear low-density polyethylene (LLDPE) as an outermost layer. However, resin properties and the manner of welding are not particularly disclosed at all. Especially, with respect to the manner of welding between a film and a discharge port, no use is made of a double molded port in the examples and the weld strength of the film and the discharge port is not specifically disclosed.
In JP-A 2008-18063 (Patent Document 5), it is stated that an innermost layer of a film for container may be constituted of a COP resin and a discharge port used may be constituted of LLDPE prepared by use of a single site catalyst, a COP resin or a multilayer thereof. However, in a weld strength test, only the weld strength of films at a peripheral portion of a container is disclosed, and no disclosure is made on the weld strength between the film and the discharge port.